1. Field of the Invention
The present invention relates to a recording medium such as an optical disc, an apparatus for recording a signal thereon, and an apparatus for reproducing a signal therefrom.
2. Description of the Related Art
In an optical recording/reproducing system, a modulation system corresponding to optical characteristics is used so as to improve recording density, signal reproducing stability, and so forth. In addition, a data formatting process, such as grouping data with a predetermined block, is performed so as to prevent a data error due to scratches of a disc or the like from propagating.
FIG. 8 shows a sector format of a conventional rewritable optical disc. As shown in FIG. 8, a sector is composed of a header portion and a data portion. In the data portion, real record data (user data) is recorded.
In the header portion, an SM (Sector Mark) 1, a VFO 2, an AM (Address Mark) 3, and an address information (ID) 4 have been recorded.
The address information (ID) 4 is composed of a track number 9, a sector number 10, and a CRC (Cyclic Redundancy Code) 11.
The CRC 11 is a code that is used to detect data errors of track No. 9 and sector No. 10.
When data is recorded on an optical disc, a desired sector is detected corresponding to the address information 4 of the header portion, which has been pre-formatted. The data is written to the data portion of that sector.
When data is reproduced from the disc, a desired sector is detected corresponding to the address information 4 of the header portion and the data is read from the data portion of that sector.
Thus, when data is recorded and reproduced, a desired sector is physically identified corresponding to the address information 4 of the header portion. Consequently, the correct reading of the address information 4 greatly affects the reliability of the system. To improve the reliability of the system, the address information 4 is repeatedly recorded in the header portion.
In recent years, due to the improvement of image compression technologies, optical discs on which digitized images and sound are recorded have become common. In the system that reproduces data from such optical discs, namely a digital video disc system, it is important to record a large amount of image data in the limited area of an optical disc. To do that, the necessity for increasing the recording density has been considered.
When a large amount of image data is very densely recorded in the above-mentioned sector format of the rewritable optical disc, many problems occur. In other words, because the address information 4 is repeatedly recorded in the header portion in the above-mentioned format, the storage of redundant information increases, which presents an obstacle to high density recording. In addition, as the recording density increases, it is predicted that occurrences of data errors increase. However, in such a format, with the address information 4, only an error is detected corresponding to the CRC 11. In other words, in the conventional sector format including the above-described sector format, high density recording cannot be satisfactorily accomplished.
As described above, when the high density recording is performed for a recording medium, such as an optical disc, some countermeasures against an error in the address information, such as sector number, are required.